Dry powder paper size having improved resistance to caking

ABSTRACT

A DRY POWDER PAPER SIZING COMPOSITION HAVING RESISTANCE TO CAKING BY ATMOSPHERIC HUMIDITY COMPRISED OF A MIXTURE OF A CATIONICALLY ACTIVE MATERIAL, A FATTY ACID AND AN ALKALI HYDROXIDE IS OBTAINED BY COATING THE FATTY ACID WITH THE CATIONICALLY ACTIVE MATERIAL PRIOR TO ITS ADMIXTURE WITH THE ALKALI HYDROXIDE.

United States Patent Office Patented Mar. 5, 1974 3,795,527 DRY POWDERPAPER SIZE HAVING IMPROVED RESISTANCE TO CAKING James N. Stone and JamesH. Wing, Augusta, and Frank B. Thomas III, Martinez, Ga., assignors toContinental Can Company, Inc., New York, N.Y. No Drawing. Filed Apr. 23,1973, Ser. No. 353,262 Int. C1. C08]: 25/02, 27/44 US. Cl. 106-206Claims ABSTRACT OF THE DISCLOSURE A dry powder paper sizing compositionhaving resistance to caking by atmospheric humidity comprised of amixture of a cationically active material, a fatty acid and an alkalihydroxide is obtained by coating the fatty acid with the cationicallyactive material prior to its admixture with the alkali hydroxide.

BACKGROUND OF THE INVENTION (1) Field of the invention This inventionrelates to a process for manufacturing a paper sizing additive which maybe incorporated in pulp stock during the manufacture of paper and morespecifically to a process for obtaining a sizing additive which may beformulated as a dry powder.

(2) The prior art In US. 3,392,085 there is described a method ofpreparing paperboard having high chemical resistance to alkalineenvironments wherein a sizing additive composed of a mixture of acationically active material and a fatty acid salt is incorporated inpaper pulp adjusted to an alkaline pH prior to the formation of the pulpinto paperboard. In practicing the method of US. 3,392,085, an aqueoussolution of the water soluble cationically active material and the fattyacid salt is added to the aqueous fiber suspension either prior to orfollowing the addition of a water soluble precipitating agent Which isadded in sufiicient amounts to provoke the forming of water insolublesoaps of the fatty acid throughout the fiber mass.

The so-treated pulp is then processed in the conventional manner forformation into paper or paperboard. Thus, the pulp having incorporatedtherein the insolubilized fatty acid salt and cationically activematerial is passed over a moving wire, whereby part of the water drainsoff, leaving a mat of fibers or wet web. The wet web is passed from themoving wire to a press section where additional water is removed, thenceto a drier section where heat is used to evaporate the remaining water,at which point further treatment may be applied (such as calendersizing, coating, etc.) before the continuous dry sheet is wound on areel or cut into individual sheets.

The paper product thereby obtained exhibits superior resistance toaqueous and alkaline environments.

The sizing additive solution of cationically active material and fattyacid salt is prepared by initially stirring about 30-50 weight parts ofa fatty acid such as stearic acid into a solution of 400-500 weightparts of water and 5-15 weight parts of an alkali hydroxide such as KOHand then heating the mixture for 5 minutes at 210 F.

The fatty acid salts prepared in this manner are then added to anaqueous solution of the cationically active material to prepare thesizing additive solution. The resultant sizing solution has aconcentration of solid additive material of about 5%.

If concentrations of greater than 5% solids are used in preparing theadditive solutions the product is extremely viscous and difficult tohandle.

The handling difficulties with sizing solutions containing high solidsconcentrations has retarded the commercial sale and utility of thesizing additive. Thus, when 5% additive solutions are contemplated forcommercial use, the high cost of shipping these dilute solutionsprohibitively increases the cost of the solutions to the user. When itis attempted to ship dry powder mixtures of the cationically activematerial, fatty acid and alkali hygroscopic nature of the alkalihydroxide causes water to be absorbed from the air on the powdermixture. A partial reaction between the fatty acid and the alkalihydroxide occurs which results in a severe caking of the additiveingredients and in some cases the formation of a solid mass. Afterdeliquescence, it is generally extremely difficult or substantiallyimpossible to satisfactorily remove the additive mixture from thecontainers in which the mixture is stored. Also, it is extremelydifficult to dilute the caked mixture with water to the properconsistency preparatory to its addition to the pulp stock.

SUMMARY OF THE INVENTION In accordance with the present invention, thereis provided an additive for incorporation into pulp stock during themanufacture of paper to impart chemical resistance thereto, the additivecombination having improved resistance to deliquescence of atmospherichumidity, comprising a dry mixture of (1) a cationically active materialselected from the group consisting of cationically active starches andgums and hydrogen bonding starches and gums (2) an alkali hydroxide and(3) a fatty acid having 12 to 20 carbon atoms, the fatty acid beingcoated with a portion of the cationically active material prior to itsincorporation in the additive mixture.

By the practice of the present invention, a homogenous blend of a drypowder sizing additive is prepared which is substantially immune todeliquescense and will not agglomerate or cake after extended storageperiods. The dry powder when dissolved in water performs equally aswell, as will hereinafter be illustrated, as the aqueous additivesolutions of 11.8. 3,392,085.

PREFERRED EMBODIMENTS The cationically active materials used in thepractice of the present invention are cationically modified starches orgums and hydrogen-bonding starches and gums. The latter, while nottechnically classified as cationic materials, behave in a very similarmanner, and are equivalent in function to the cationically modifiedstarches and gums used to prepare the sizing additives of the presentinvention.

A wide diversity of cationically active materials are available to theart and disclosure of those more useful in the practice of the presentinvention may be found in US. 3,392,085, the disclosure of which isincorporated herein by reference.

Cationically modified starches and gums are obtained by modifyingnaturally occurring starches and gums so that they exhibit a cationiccharge, i.e., a positive charge, when dissolved in aqueous medium.cationically modified starches and gums are conveniently obtained by thereaction of naturally occurring starches such as corn starch and potatostarch with an etherification agent such as dialkyl aminoalkyl epoxidesor dialkyl aminoalkyl halides following the procedures of US. 2,813,093and 2,917,- 506, or epichlorohydrin and a tertiary amine following theprocedure of US. 2,876,217.

Many cationically modified starches and gums which may be employed foruse in the present invention are available commercially.

A cationic corn starch is sold by National Starch and Chemical Corp.under the trademark Cato 8. A cationic potato starch is sold by A. M.Menickle and Sons, under the trademark Epic-N.

The cationically modified gums which may be employed in the presentinvention are extracts from vegetable saps, seeds and seaweedsynthetically modified. according to the same procedures used to renderstarches cationically active. Illustrative of such gums are locust beangums, guar gums, kararya gums, agar and alginates.

A cationically modified galactomannan gur gum is sold by Stein, Hall andCompany, Inc., under the trademark Draybond II.

Hydrogen bonding starches and gums may be extracted from theirrespective vegetable origins and used directly in the practice of thepresent invention and other nonhydrogen-bonding gums may be rendered soactive by chemical treatment.

The naturally occurring hydrogen bonding starches and gums arecharacterized in that there are numerous hydroxyl groups on themonosaccharide units and these are sterically arranged so thathydrogen-bonding occurs between the chains. Such. hydrogen-bonding isgenerally attributed to the presence and behavior of these hydroxylgroups.

Tamarand seed flour is an example of hydrogen-bonding gum havingcationic-type propertes and is composed of glactose, xylose and glucoseunits in the approximate molar ratio of 1:2:3, and is sold by DycolChemicals, Inc., under trademark Dycol D-16.

Another hydrogen-bonding gum is that obtained by extraction from theguar plant. While this guar gum may be employed in the present inventionas the cationic material, it may also be chemically treated to attain acationic charge such as by the etherification processes used for thestarches.

Guar gums in unmodified form, as well as those in cationic form, aremarketed by Stein, Hall and Company, Inc., under the trademark Jaguar.

Locust bean gum may also be employed as a hydrogen bonding, naturallyoccurring galactomannan.

The fatty acid employed in preparing the additive compositions of thepresent invention may be any one or a mixture of a saturated fatty acidshaving from 12 to 20 carbon atoms. Illustrative saturated fatty acidsinclude lauric-Ciz, tridecylic-C myristic-C pentadecylic-C palmitic-CmargariC-C stearic-C nondecylic-C and arachidic-C Various mixtures ofthese fatty acids may be commercially obtained and the commercialproducts usually contain some proportion of unsaturated fatty acids. Forbest results, the amount of unsaturated fatty acid component should notexceed 30% by 'weight of the fatty acid and preferably the fatty acidshould not contain greater than 7% unsaturated fatty acids. Variouscommercially obtainable fatty acid mixtures which may be employed in theadditive compositions of the present invention are sold by ArmourIndustrial Chemical Company under trade names: Neo-Fat 18s, Neo-Fat58-59; and Darling and Company under trade names: Dar-Hy, Dar-C andDar-S77. These commercial mixtures are generally low in unsaturatedfatty acid content and contain greater than 80% of at least one or amixture of stearic, palmitic, margaric and myristic acids.

The alkali hydroxides that may be used in preparing the dry additivepowers of the present invention are the water soluble hydroxides namelysodium, potassium and lithium hydroxides.

In preparing the dry powders of the present invention the amounts ofcationically active material and fatty acid powder required in theadditive mixture are .dry blended, using a suitable blending means suchas a rotary blender, for a time sufficient to cause the complete coatingand encapsulation of the fatty acid by the cationically active material.Thereafter rial coated fatty acid is mixed with the alkali hydroxide toprepare the dry additive mixture of the present invention.

The dry powder additive mixture of the present invention is generallycompirsed of about '65 to 75% by weight of the fatty acid, about 15 to20% by weight of the cationically active material and about 10 to 20% by.weight of the alkali hydroxide.

In adding the additive mixture to paper pulp, the mixture prior to itsaddition to the pulp is dissolved in water by adding the mixture towater at a concentration of 1% to 10% by weight based on the Weight ofthe water and then heating the water additive combination at atemperature of 175-200 F. for 10 to 60 minutes. The fatty acid salt ofthe alkali hydroxide forms concomitantly with the dissolution of the drypowder mixture in the heated water. I

After dissolution and formation of the fatty acid salt, the aqueoussolution containing the cationically active material and the fatty acidsalt is added to the proper pulp whereupon the salt is insolubilized onthe paper fibers using a precipitating agent.

The cations of the insolubilized fatty acid salts are desirably aluminum(Al ferric (-Fe and/ or chromic ions (Cr i The precipitating agent whichis employed for insolubilizing the water soluble saturated fatty acidsalts are water soluble inorganic metal salts of polyvalent metallicions such as aluminum ferric and chromic. Illustrative of these saltsare aluminum sulfate, aluminum chloride, potassium sulfate-aluminumsulfate salts, ferric sulfate and chromic sulfate. The aluminum sulfateand potassium sulfate-aluminum sulfate salts, normally referred to asalums, are preferred in the practice of the present invention. The alumemployed may be anhydrous alum,

Al (SO paperrnakers alum, Al (SO 18H O QIMTCOIII mon alum, -K SO Al- (SO-24H 0. When the term alum" is employed in the working examples below,paper makers alum is intended. The precipitating agent is added to thepulp suspension in an amount which will create'f ance with the sizingadditive of the present invention may be made up with refined fiberssuch as bleached-and unbleached fibers, ground wood, soda pulp fibers,semi-' chemical fibers, kraft fibers, sulphite fibers, textile andsynthetic fibers, such as viscose rayon and cellulose acetate, and othercellulosic fibers. The pulp is generally re-.

fined to a Canadian Freeness value of from 400-700 milliliters beforeaddition of the sizing additive. The pulp consistency is normally 0.3 to3.0 percent by weight, although considerable variation is possible.

.The cationically active material is, added .to the pulp suspension at aconcentration of 0.10 to 6.0%based on the weight of the solids contentof the suspension and preferably 0.70 to 2.0% by weight of the solidscontent of the suspension. The water soluble fatty acid salt is added tothe pulp suspension at a concentration of 0.10 to 10.0% based on theweight of the solids content of the pulp suspension and preferably0.50.to 6.50%- by weight of the solids content of the suspension.

The following examples further illustrate the practice of the presentinvention; however theexamples are not to be construed as limiting thescope of the invention.-

EXAMPLE 1 A series of handsheets were made on a Noble and StandardFreeness of '495 milliliters, a pulp consistency of 1% and a pH of6.85-7.05. The pH of the refined pulp was adjusted to a pH or 8.0-8.05wartime.

In a series of tests, the sizing additive was added to the pulpsuspension in amounts of 0.09% by weight (based on the weight of thesolids content of the suspension) Cato 8, a cationic corn starch and0.41% by weight (based on the weight of the solids content of thesuspension) potassium stearate and the pH of the suspension was loweredto 6.0 with 0.59% by weight (based on the dry weight of the fibers)alum. This amount of alum was sufiicient to completely precipitate thestearate salt on the pulp fibers.

Three Cato-S-potassium stearate sizing solutions were used in the testseries. The three solutions were prepared in the following manner.

Sizing solution 1 was prepared in the following manner:

86.2 pounds of stearic acid beads and 21.5 pounds of Cato 8 powder weremixed for 30 minutes in a concrete mixer. This period of time wassufiicient to completely coat and encapsulate the stearic acid beadswith the Cato 8. Thereafter 17.2 pounds of potassium hydroxide granuleswere added to the Cato 8 coated stearic acid and the mixing wascontinued for an additional 30 minutes to blend the potassium hydroxidewith the Cato 8 coated stearic acid. The dry powder blend was thenstored in polyethylene lined multiwall paper bags. After 4 Weeks, 2pounds of the powder mixture were removed from the bags. It was observedthat the powder had a slight yellowish tint. This dry powder additivemixture was then added to water at a concentration of 5% by weight andheated at 190-195 F. for 30 minutes before being added to the pulpsuspension.

Additive solution 2 was prepared in the same manner as solution 1 withthe exception that solution 2 was not stored prior to its dissolution inwater.

Additive solution 3 was also a 5% solution of Cato 8 stearic acid andpotassium hydroxide but was prepared by heating 26.1 grams of KOH with130.6 grams stearic acid at 190 F. for 5 minutes and then adding thereto32.6 grams Cato 8.

After formation in the handsheet mold, the handsheets were conditionedat 50% relative humidity at 73 F. for 24 hours prior to being subjectedto physical testing. The results of these tests are recorded in Table 1below.

Watcr drop tcst-Distilled water is dropped onto the paper from adistance of 3 inches and the time in seconds for a single drop (0.05 cc.to be completely absorbed is recorded.

2 Cobb test-Evaluated according to TAPPI Standard '1 441 05-63, feltside exposed to water.

3 Caustic drop test-A single drop (0.05 cc.) 5% N aOH is dropped ontothe paper surface from a distance of 3 inches and the time {or the dropto be completely absorbed into the paper is recorded.

4 Bursting strength of paper-Evaluated by TAPPI 20 Standard T 403 ts-63,150 clamp pressure.

The results recorded in Table I indicate that there is no significantdifference in the sizing effectiveness of additive solutions preparedfrom a dry powder blend of the components (solutions 1 and 2) or anaqueous solution prepared-in the manner of the prior art (solution 3)nor is there any loss in size effectiveness or paper physical propertieswhen the dry powder mixture is stored for an extended period of time(solution 1).

EXAMPLE 2 The procedure of Example 1 was repeated with the exceptionthat the pulp used was 84% pine pulp and 16% hardwood pulp beaten to aCanadian Standard Freeness of 437 mls. and a consistency of 2%. Thephysical test results of the handsheets prepared in this manner weresimilar to those of Example 1 and are summarized in Table II below.

TABLE II Paper physical properties Solution number 1 2 3 Oven dry basisweight, 1b./m s.f 48. 8 48. 7 48. 5 Caliper, 1/1,000 inch 15. 6 15. 014. 9 Density lb./pt 3.13 3. 25 3. 26 Distilled water drop, seconds3,888 4, 226 4, 202 2 minute Cobb, grams/m. 35. 6 37. 1 37. 8 Burst,p.s.i 149 176 171 What is claimed is:

1. An additive for incorporation into pulp stock during the manufactureof paper to impart chemical resistance thereto, the additive combinationhaving improved resistance to deliquescence of atmospheric humidity,comprising a dry mixture of (1) a cationically active material selectedfrom the group consisting of cationically active starches and gums andhydrogen bonding starches and gums, (2) an alkali hydroxide, and (3) afatty acid having 12 to 20 carbon atoms, the fatty acid being coatedwith a portion of the cationically active material prior UNITED STATESPATENTS 2,129,919 9/1938 File 106--311 3,392,085 7/1968 Oliver 106-2112,914,412 11/1959 Stephan 106211 2,239,814 4/1941 Edson 106212 653,7767/1900 Milligau 106-212 THEODORE MORRIS, Primary Examiner US. Cl. X.R.

